As a feed apparatus, conventionally, the feed apparatus disclosed in the Japanese Unexamined Patent Application Publication No. 2001-47342 is known, for example. This feed apparatus is provided on a vertical machining center having, as primary components, a bed, a column, a spindle head, a spindle, a saddle, a table, etc., and moves the spindle head that is a movable body with respect to the column that is a stationary body in the vertical direction.
Specifically, this feed apparatus comprises a ball screw disposed on the column in such a manner that its axis extends in the vertical direction and it is rotatable about its axis, a servo motor disposed on the column for rotating the ball screw about its axis, a transmitting mechanism for transmitting the rotational force of the servo motor to the ball screw, a nut fixedly provided on the spindle head and screwed onto the ball screw, and a controller for supplying a drive current to the servo motor and feedback controlling the servo motor.
In this feed apparatus, when a drive current is supplied from the controller to the servo motor and the servo motor is thereby rotated, the rotational force of the servo motor is transmitted to the ball screw via the transmitting mechanism and the ball screw is thereby rotated about its axis and the nut is moved along the ball screw. Thereby, the spindle head is moved up or down.
It is noted that, in the vertical machining center, there are provided, in addition to the above-described feed apparatus, a feed apparatus having a similar configuration as that of the above-described feed apparatus and moving the saddle in a horizontal direction and a feed apparatus having a similar configuration as that of the above-described feed apparatus and moving the table in a horizontal direction orthogonal to the moving direction of the saddle.